Abstract:To explore the differences in carbon emissions over the whole life-cycle of different building structures, the published calculated carbon emissions from residential buildings in China and abroad were normalized. Embodied carbon emission flows, operations stage carbon emission flows, demolition and reclamation stage carbon emission flows and total life-cycle carbon emission flows from concrete, steel, and wood structures were obtained. This study is based on the theory of the social cost of carbon, with an adequately demonstrated social cost of carbon and social discount rate. Taking into consideration both static and dynamic situations and using a social discount rate of 3.5%, the total life-cycle carbon emission flows, absolute carbon emission and building carbon costs were calculated and assessed. The results indicated that concrete structures had the highest embodied carbon emission flows and negative carbon emission flows in the waste and reclamation stage. Wood structures that started the life-cycle with stored carbon had the lowest carbon emission flows in the operations stage and relatively high negative carbon emission flows in the reclamation stage. Wood structures present the smallest carbon footprints for residential buildings.
The longitudinal and directional stability of flying wing UAV is poor, the coupling of triaxial force and torque is serious, and the control surface is special, so the flight control is difficult and the control law is complex. Taking a flying wing UAV as an example, the control laws of track tracking based on dynamic inverse control method and control allocation are designed. The applicability of traditional stability margin excitation method based on signal generator and pilot’s manual control is analyzed, and a stability margin excitation method based on three-a2xis control decoupling is proposed, which is verified by simulation. The results show that the stability margin of the designed three-axis dynamic inverse control law system meets the requirements, and the stability margin excitation method based on three-axis decoupling is suitable for the stability margin analysis of three-axis coupled UAV.
This paper presents the current situation that the pilot’s manual operation method can’t fully meet the requirements of UAV flight test. To solve the problem, a UAV flight test technology based on embedded command is proposed. By analysing the verification contents and assessment methods of UAV flight test, the typical actions in UAV flight test are extracted, the embedded command modules are designed, and the embedded command flight test method is formulated. The flight test results show that compared with the manual operation method, the embedded command flight test technology can alleviate pilot’s operation burden, reduce the flight test risks and improve the flight test efficiency.
Flight mode characteristics of free flight model with four propellers are analyzed, based on the results and flight test requirement, the control law is designed, then the simulation model is established and analyzed, finally, the control law is applied to free flight model test.The flight test results show: the propeller promoted the velocity stability and Dutch mode characteristic; level and turn flight stall test subjects were effectively accomplished based on the control law; the dynamic model built can simulate the free flight model test processand initially predict the stall characteristics; level stall angel is 10-12°, turn stall angel is 8-10°.
According to the requirements of boundary layer transition detection measurement flight test, the study on the detection technique of infrared thermal image in real flight conditions was carried out. In this paper, the basic principle of infrared measurement technique was introduced firstly. Through the analysis of the main factors, such as emissivity, radiation incidence angle and temperature difference between the measured object and environment, the test means were determined, which includes surface treatment, infrared light path adjustment, solar radiation and internal heating of tested parts. Then the whole flight test method of boundary layer transition measurement was designed, including selecting test object and test instrument, determining test procedure and image processing procedure, and giving transition location criterion. Finally, the validity of this flight test method was demonstrated through testing results, the research of which would be helpful and meaningful in boundary layer transition measurement.
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